The particle bound mercury (PBM) in urban-industrial areas is mainly of anthropogenic origin, and is derived from two principal sources: Hg bound to particulate matter directly emitted by industries and power generation plants, and adsorption of gaseous elemental mercury (GEM) and gaseous oxidized mercury (GOM) on air particulates from gas or aqueous phases. Here, we measured the Hg isotope composition of PBM in PM10 samples collected from three locations, a traffic junction, a waste incineration site and an industrial site in Kolkata, the largest metropolis in Eastern India. Sampling was carried out in winter and monsoon seasons between 2013–2015. The objective was to understand whether the isotope composition of the PBM represents source composition. The PBM collected from the waste burning site showed little mass independent fractionation (MIF) (Δ199Hg = +0.12 to -0.11‰), similar to the signature in liquid Hg and Hg ores around the world with no seasonal variations. Samples from the industrial site showed mostly negative MDF and MIF (δ202Hg = -1.34 to -3.48 ‰ and Δ199Hg = +0.01 to -0.31‰). The MDF is consistent with PBM generated by coal combustion however, the MIF is 0.15‰ more negative compared to the Hg isotope ratios in Indian coals. The traffic junction PBM is probably not produced in situ, but has travelled some distances from nearby industrial sources. The longer residence time of this PBM in the atmosphere has resulted in-aerosol aqueous photoreduction. Thus, the MIF displays a larger range (Δ199Hg = +0.33 to -0.30‰) compared to the signature from the other sites and with more positive values in the humid monsoon season. Different Hg isotopic signature of PBM in the three different sampling locations within the same city indicates that both source and post emission atmospheric transformations play important roles in determining isotopic signature of PBM.

Lead has been central to technological development for centuries; however, its release into the environment and subsequent human exposure pose significant public health risks. The review presented here critically assesses the contemporary environmental lead risk as global lead production and use are rapidly increasing, largely driven by the rising demand for electrification. We show that environmental lead exposure persists today due to legacy contamination, ongoing coal usage, and insufficient protection of workforces during production, use, and recycling of lead-acid batteries and other lead-containing products, particularly in low- and middle- income countries. We estimate that contemporary childhood lead exposure alone leads to an annual global economic loss exceeding $3.4 trillion (2021 US dollars adjusted for purchasing power parity), with pronounced disparities between high- and low- and middle- income countries. To prevent a large-scale resurgence in lead exposure, we identify four critical areas for urgent policy intervention.